Drawbridge



Feb. 22 1927.

"r E. sRowN DRAWBRIDGE '2 Sheets-Sheet 1 Filed March 1. 1923 Feb. 22 1927.

v T. E. BROWN DRAWBRIDGE 2 Shets-Sheet 2 Filed March 1. 1923 -INVENTOR 2W 5. Kym/ Patented Feb. 22, 1927.

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Application filed March 1, 1823. SerialNo, 622,053.

This inventionrelates to that type of i cule bridge which has long been known" as the .idrawbridge, and which consists es sential'ly of a pivoted movable span with balancing beams pivotally supported above the bridge and connected at their outer ends to the movable span by tensional connections, balance being. effected bypheavy weights "attached to the inner, ends, of said beams. j

In my copending application, Serial No. 5.57, t4=2,'file d- April 29th, 1922,. I'show and describea single leaf bridge, and this inve'ntion refersv more particularly to double leaf bridges of similar type. V g

The principal object of my invention is to suspend each movable ,leafas a cantilever by means ofthe connections from-the, leaf-to the balance beams which usually serve as balancing connections only, and enable said connections to sustain not only the dead weight of the leaf but to sustainralsfo the liveyload carried on. theleaf, and this I do by aidpof the weight, of the counterweight itself, and am enabled thereby todispense with the foldinghangers, hooks from beam to span and other devices heretofore used, and so greatly simplify the structure.

Another object of my invention is toneutralize; the heavy horizontal trunnion thrust, due to the combined live and dead. loads on the, leaf, bjy intersecting the main tower members; at the level of the trunnion or pivot of the leaf, whereby moments from the trunnion; thrust are avoided. and theQusua-l auxiliary members required to resist such moments may be omitted, and also the, re sultant of the vertical forces at thechannel pier is moved back from the trunnion and therefore the channel pier may beset back from under the trunnion, enabling shorter leaves to be used in proportion to the required clear channel width, and especially so when deep and massive foundations are required. I p

The means of accomplishing these aswell as other objects of my invention will be understood from the description and the drawings.

Referring to the drawings:

Fig. 1 is a side view of-one-half ofa dou ble leaf bridge of my invention.

or Fig. 4. a Y

' nection or hanger for truss 1.

detail.

v 1* 1g. 2 is an end view at larger scale of a portion of Fig. 1.

Figs. 3 and 3? show modifications of the arrangement shown in Figl i Fig. 4' is a side view" at a a portion offFig. 1.

4 is'a plan view ofFig. 4. I

Fig. 5 is an end View, in partial section,

Fig, dis a side view of a special form of trunn on. i

Fig, T is an end view of. Fig. 6, and Fig. 8 shows my inventionas applied to abridge having long approachspansi 1 Similar characters, refer to similar parts in all the figures. v 7' i I I I Referring more especiallyjto Fig. 1, in

which it will'be understood that only the lefthand end of the structure isfshowii and that the structure is repeated on the right handend, the broken line Z%Z representing the'centreline of the, river channel; A is a V .movable leaf of a bascule bridge,and a fixed or tower span. 1 is a truss of said leaf A and 2 the trunnion or pivot abfout which'it rotates. 4L and Q1Te piers supporting the bridge. The fixed span B- comprises the member 7and posts 8' and 'QQand; base 3. Said base 3v carries the trunnion 2, of the movable leaf A, and said posts 8'and Q carry the pivot 10 of the balance: beam 11, and form with said member, 7 a toweror counter; weight carrying frame.'.

6 is an additional post which supports the forwardend of beam 11, when leaf "A is in its lowered position, by means of seat 19 and bearing 20, said seat 19 being fixed on post 6, and said bearing 20 forming, part of beam and moving with it. Post 6 is. held inrposition by brace 21.

On the inner or, shore end of the balance beam 11 and carried bysaid beam is the counterweight 12, and at, the otherfend of said beanill is a pivot 13 to which is connected the short linl; 14; which in turn is connected by pivot 15 to thelong link 16, said long link 16 being connected 'to' the truss 1 by the pivot 17 saidshort'link 14.

together with long link 16 forming a conr rasci s f lit) 18 a stop, suitably placed on beam ll, to arrest the rotation of link 14 about pivot 13. Thus rotation of the links 11 and 15, duringthe first portion of the movement of the span 1, takes place about pivot 13 and so continues until said link 1 1 contacts with stop 18, after which rotation of link 16 takes place about pivot 15, and the positions of said pivots 13 and 15 and stop 18 are such that the counterweight substantially balanees the mt *able leaf A in all its positions.

The inclined posts (5 and 9 terminate at their lower ends at substantially the same level as the trunnion 2, said post 6 being located su'lliciently tar heel; of the trunnion to permit of full opening of the leaf A withoutinterference of truss 1 with post 6, the said post 6 and post 9 being preferably in line with truss 1, i. 0., all having the same plane of symmetry as shown in Fig. at.

Dotted lines show the movable span in its fully open position, and also the counterweight in its corrcsponi'ling, lower position. It will be understtmd that in general the description refers to one side of the bridge only and that the parts described will usually be duplicated on the other side of the bridge. 1

The required location of pivots 13 and 15 and stop 18, to cause the counterweight to balance the mo able leaf in all its positions, may be delerlnined by the method described in my copending application hereinbeiore referred to.

The bridge may be operated in any suitable manner, as by rack .32 and pinion 2.3 and by any suitable motor and mechanism adapted to rotate said pinion 223, also any of the usual forms of shear locks may he used if desired to lock the toe ends of the trusses 1 together where they meet at the centre of the channel Z-Z.

It will be seen by reference to Fig. 1, that with my construction the angular motion of the beam and its counterweight is not equal to the angular motion ot the leaf and hence when the span is in its vertical position the counterweigrht 1:2 remains outside oi the cmintcrweig ht, supporting :lramc" and 1 am enabled therefore toplacc the countcrweigrht 1'2. beam ll, posts (3. R and and scat 19 all in the same plane and hence said bearing 20 contacts with seat 19 and beam 1.1 is supg'iorted by post (3, hanger 16 thus supporting teal l a cantilever. when said lent is in its lowered position as shown in Fig. '1, and by choosing a suitable meition for the beam trunnion 10 said seat 19 may be placed so far t'orwa rd of said beam trunnion 10 and so close to the hanger 113 that the moment of the counterweight; about said seat 19 when the leaf is in its lowered position is greatly in excess of the moment about seat 19 of the combined live and dead loads carried by the hangers 16 so both the live and dead loads of the least are sustained by said hanger and the leaf is positively supported under said loads by means of the weight of the counterweight itself, and the folding, or detachable members usually used are no longcr required.

While my construction admits of, and I prefer placing the beam 11, post 6, and seat 19, all in the same plane, as shown in the partial end view Fig. 2*I do not confine myself to this construction, :for as shown in Fig. 3, when for any reason the beam 11" and the counterweight supporting frame together with post (3" are not in the same plane I may use a cross girder E24" and place seat 19 on said cross girder 2 1-" as shown in Fig. 3. \Vhen as shown in Fig. 3" beam ll is outside of post 6, seat 1.9 may be placed on an extension of girder 241-; i

In d aw bridges it is ad uintageous to place the trunnion 2 of the movable leaf 1. at or preferably slightly above the floor level as thereby serious con'iplications at the heel tloor break are avoided, and thus the trunnion 2 (see Fig. l) is usuallyat a consider able height above the bridge pier l. See also Figs. 4: and 5. i i

In double leaf bridges of the kind described the trunnion thrust is great and is substantially horizontal, the Vertical components of said thrust, it any, being but a small proportion of the horizontal components. I therefore prefer to place the apex a? of the tower members 6, T and 9, i. o. the point oi intersection ot the centre lines of said members, at the level of the trunnion 2, as thereby moments from the horizontal trunnion forces are avoided, and the vertical resultant of the forces in said members which constitutes the load on the bridge pier 1 co incides with the apex a, therefore said pier ll may he placed under said apex (0 instead of under trunnion 2, thereby enabling fender to be placed further from the centre of the channel thus widening the channel of a double leaf bridge by an amount equal to twice the distance between the apex a and the trunnion 2, for, as will be clearly seen from Fig. 1, were pier l1 placed under trunnion 2--thcn tender 2% would be pushed out and encroach on the channel and this cucroachment would occur on both sides of the channel. Conversely, therctore (with an cstublii'shed cl'lanncl width) my construction permits ot the leaves being made shorter than in the usual construction in which the pier is under the trunnion. This results in i known as gusset plates), and I provide short members 26 and 27 to act as stitr'eners :tor

i an

said gusset plates, and, if preferred, stiffening angles 28 inayrbensedon the edges of i P ates 1 In' bridges of large size carrying very heavy loads it may sometimes be desirable to avoid carrying. the live load" "thrust through the trunnion In such cases (see Figs. 6 and 7) I prefer to use a separate or live load bearing 29 below the trunnion, and support the bearings 32 of trunnion 2 on a pin thus pivotally supporting trunnion 2, so said trunnion is slightly movable, as thereby ambiguity of stress from deflection of the movable span under the live load is avoided.

Referring to Fig. 8n1y construction is specially applicable when, instead of short tower approaches, the approach spans B are long. In such cases, I prefer to so arrange the counterweight 12 and balance beam 11 that they may remain always above the approach span duringthe motion of the moving leaf A and'I may place the seat 19 on the inclined end post 6 of' the long approach spans B. In such cases the method of determining suitable arrangement of hanger 16 and its connecting links to effect a proper balance of the moving leaf will be understood from my copending application hereinbefore referred to and other patents cited the-rein. a

A very light bridge may possibly be subjected to a live load heavier than theweight of the counterweight will sustain. In light bridges I prefer to use a stop 31, as shown in Fig. 8, said stop adap'ted to contact with and hold 'down the rearward end of beam 11 should the live load on themovable leaf be sufficient to overcome the counterbalance weight and tend to lift the beam trunnion 10 out of its bearings, and in the form shown in Fig. 1, in which the tower members end under pivot 10, I accomplish a similar result by extending the tower gusset plates above and over pivot 10 forming a stop 31. Now, having described my invention, what I claim is: V

l. A drawbridge comprising a movable leaf, a balance beam carrying a counterweight, a stop for the beam and a single connection adapted to transmit the weight of the leaf to thebeam and adapted also to support the leaf in its lowered position from the beam.

2. A drawbridge comprising a movable leaf, a balance beam carrying a counterweight, a connecting member between said leaf and said beam and means for supporting the beam between its pivot and the point of attachment of said connecting member when the leaf is in its lowered position;

3. In a drawbridge comprising a movable leaf, a balance beam carrying a counterwei htaframe su ortin said beam and a connection between said beam and said leaf,

aseaton saidframe adaptedto contact with In a clra wbri dge comprising a fixed part a movable leaf-,a balance beam'carrying a counterweight and a connection between said beam a'ridsaid-leaf; stop on said fixed part adapted to prevent further movement of said beam whereby said leaf, when in its lowered position, is positively supported by said connection.

5. In a drawbridge, the combination of a movable leaf, a balance beam carrying a counterweight, a frame supporting said beam, a connection between said beam and said leaf, and a seat on said frame adapted to contact with said beam and prevent further movement of said beam when said leaf is in its lowered position.

6. In a drawbridge, a movable leaf, a balance beam, a counterweight on the rearward end of said beam, a frame carrying the pivot of said beam, a connection between said movement of said leaf.

7. In a drawbridge, a movable leaf, a balance beam carrying a counterweight and a connection between said beam and said leaf and a fixed part having a plurality of points of support for said beam, one of said points of support arranged to cause the counterweight to sustain the live loadon said leaf.

8. In a drawbridge, a movable truss having a'pivot at its heel, a fixed counterweight supporting frame having an inclined post adjacent to said pivot, said post and said truss lying in the same vertical plane, said inclined post and co-acting members of said frame having their apex behind said pivot and substantially distinct from and at the level of said pivot, a base connecting said members and said pivot, a pier supporting said base and said pier centrally placed under said apex.

9. In a drawbridge, comprising a movable leaf having trusses at each side thereof, a

support for said movable leaf having trusses at each side thereof, the trusses of said movable leaf and the trusses of said support being in the same vertical plane, trunnions 'movably connecting the trusses of said leaf said frame adapted to eoutact with said leu'f, a movable structure carrying at counterbeam when said leaf is in its lowered posiweight, a stop forsaiclstructure and a sintion and at stop to prevent undue upward gle connection adapted to transmit the 10 movement of said counterweight should weight of the leaf to said structure and 5 overloading of said leaf lift said counteradapted also to support the leaf in its lowweight. ered position from said structure.

ll A drawbridge comprising a movable THOMAS E. BROWN.- 

